Here is the full list of all 26 Serious Sam VR: The First Encounter achievements.
Frag a total of 100 players.
Win a versus match.
Complete the game.
Complete the game in single player by beating the estimated time on each level.
Complete the game in single player on unmodified serious difficulty.
Complete the Metropolis level in single player on unmodified serious difficulty.
Complete the game in co-op on unmodified serious difficulty.
Trigger Ugh-Zan's regeneration.
Pierce at least 10 enemies with a single cannonball.
Kill 100 Enemies with the Cannon.
Leap into the unknown on Luxor.
Defeat the Lava Golem boss.
Kill 150 Enemies with the Rocket Launcher.
Kill 300 Enemies with the Minigun.
Obtain the Water Element.
Kill 200 Enemies with the Thompson Submachine gun.
Kill 20 enemies with the Minigun without releasing the trigger.
Kill 250 Enemies with a shotgun.
Obtain the Fire Element.
Obtain the Earth Element.
Find at least 10 secrets in single player.
Pull out a single Colt and immediately deliver a killing shot.
Obtain the Air Element.
Complete any level in co-op.
Complete a level in co-op with blood option set to hippy.
Complete any level in single player.